Process for the manufacture of azo dyestuffs



" UNITED S ATES 1 PATENT; OFFICE PROCESS F Society of Chemical Switzerland P No lirawing. Applicati No. 9,900. In Switze In Patent No 1,871,946 there is described a B THE MANUFACTURE OF AZO DYESTUFFS Grald Bonhote, Basel, Switzerland, assignor to Industry in Basle, Basel,

on March 7, 1935, Serial rland March 22, 1934 A 4 Claims. (01. 260-95) series of dyestuffs which dye violet tints and are obtained by the coupling of an arylide of 2,3 -hydroxynaphthoic acid with a diazo-compound of 5 the, general. formula 11-0 ore-'0 Q-NHQIhN-OH in which R is an aromatic nucleus of the benzene series and both X's In the further working of has been observed that while ponents in which both Xs are alkoxy-groups.

this invention it these diazo-comstand for OCH3 couple easily, considerable diificulty attends the coupling in the case of diam-components in which both Xs stand for 0CzHs-groups.

If the coupling is conducted in a medium acid with acetic acid the dyeings produced by the dyestuffs are weak and unsightly; if the coupling is conducted in neutral or feebly alkaline medium,

such as a medium alkaline with bicarbonate of soda, the dyeings especially these on yarn,

are stripy and, in consequence of the decomposition of the diazo-compound the dye-bath becomes turbid.

This invention relates to a process of making dyestuffs in substance or on the fibre of the constitution in question which yield unobjectionable dyeings by conducting the coupling in a liquid which, by suitable addition, retains a pI-I-value which is always does not exceed 6.5 but below 4.8. Thus the invention dition to the coupling solution markedly below I that is to say does not substantially fall comprises the adof a buffer agent such as a mono-alkali salt of phosphoric acid and products of similar action whose pH-value lies about 5. Such bufier agents are for example the alkali salts of citric acid, mixtures tassium salts of phthalic acid of mono-powith sodium hydroxide, mixtures of mono-alkali salts of maleic acid with dialkali salts of the same acid. This expedient leads to valuable results not only in the case of arylides of 2,3-hydroxynaphthoic acid but also in the case of other carboxylic acids, for instance hydroxyanthracene-carboxylic suitable hydroxythe arylides of 2,3-

acid. The addition of the bufier agent is also of value in the case of those diazo-co-mponen ts in which both Xs stand for OCI-Ia. As already stated the coupling of these diam-components occurs more eas-- ily than that of the corresponding ethyl bodies; by use of the buffer substance the dyestuff obtained produces dyeings which are of,equally 5 good yield as those obtained with dyestuffs produced in neutral or feebly alkaline media; however, the baths remain completely clear when the buffer agent is used.

The following examples illustrate the invention:---

Example 1 Cotton yarn is impregnated with a solution containing per litre 5 grams of 2,3-hydroxynaphthoic acidl-naphthalide, 14 cc. of caustic 15 soda lye of 34 B., 10 cc. of Turkey red oil and '7' cc. of formaldehyde solution of 40 per cent. strength, then well wrung out and developed in a diazo-solution containing per litre the diazocompound from 2 grams of 4-(4-methyl)-phenoxya-cetyl-amino-Z,E-diethpxy-1- aminobenzene and 8 grams of primary potassium phosphate. 7 There is obtained a pure blue tint. The procedure is similar when other diazotizable bases are used, for instance 4-phenoxyacetylamino- 2,5 -diethoxy- 1 -aminobenzene, 4- (4-chloro) -phenoxy acetylamino2,5-diethoxyl-aminobenzene, 4-(2- or 3 methyl) -phenoxyacetylamino-2,5-diethoxy 1 aminobenzene and when other arylides of 2,3-hydroxynaphthoic acid are used, for example the anilide, the metatoluidide, the meta-chloraniline of 2,3-hydroxynaphthoic acid.

Example 2 Cotton yarnris impregnated with a solution containing per litre 4 grams of 2,3-hydroxynaphthoic acid-4'-ethoxyanilide, 8 cc. of caustic soda lye of 34 B., 10 cc. of Turkey red oil and 5 cc. of formaldehyde solution of 40 per cent. strength, well wrung out and developed in a diazo-solution containing the diazo-compound from 2 grams of 4-(4'-methyl) -phenoxyace:- tylammo-2,5-dimethoxy-l-aminobenzene and 10 grams of primary sodium phosphate per litre. There is produced a pure violet tint and the coupling bath remains completely clear.

Like results are obtained in printing or in dyeing piece goods. Other arylides of other acids may be used, for example the arylides of 2,3-hydroxyanthracene-carboxylic acid.

What I claim is:-

1. A manufacture of dyestuffs in substance or on the fibre consisting in coupling a diazo-compound of the general formula in which R is an aromatic nucleus of the benzene series and both Xs stand for alkoXy-groups, with an arylide of the 2,3-hydroxynaphthoic acid, in a medium whose pH-value does not exceed 6.5 and does not fall substantially below 5.

3. A manufacture of dyestuffs in substance or on the fibre consisting in coupling a diazo-compound of the general formula in which R is an aromatic nucleus of the benzene series and both Xs stand for alkoxy-groups, with an arylide of the 2,3-hydroxynaphthoic acid in a medium buffered by addition of a monoalkali metal salt of phosphoric acid.

4. A manufacture of dystufis in substance or on the fibre consisting in coupling a diazo-compound of the general formula 0 CaHl in which R is an aromatic nucleus of the benzene series, with an arylide of the 2,3-hydroxynaphthoic acid, in a medium buffered by addition of a mono-alkali metal salt of phosphoric acid.

GERALD BONHOTE. 

